Numerous examples can be cited wherein some sort of fluid-tight seal is either desirable or necessary. In the medical field, for instance, fluid-tight seals are required for medical devices whenever there is a need to either prevent the loss of fluid or prevent fluid from becoming tainted by contact or interaction with a contaminant. Regardless of the particular application, however, the problems which must be overcome to establish a fluid-tight seal are particularly troublesome when the seal is required between elements that move relative to each other.
Not surprisingly, advances in any particular technology frequently involve new developments in related technologies. For example, many related but different developments have been made in the atherectomy field. Very briefly, atherectomy devices are used in vascular surgery to open stenotic segments in arteries by removing plaque from the arterial wall. In performing such surgery, atherectomy devices have some unique requirements which result from their mechanical requirements. Specifically, atherectomy devices have rotating parts which must be able to function simultaneously both inside and outside the body without causing an excessive loss of blood. For example, the atherectomy device disclosed in co-pending application Ser. No. 213,691 for an invention entitled "Cutter for Atherectomy Device" and which is assigned to the same assignee as the present invention, requires the rotation of a cutter element inside an artery by an external drive unit to excise the plaque from the artery. Since both the rotating cutter and the rotating drive shaft must be positioned within the artery and operated by apparatus external to the body, there is a need to provide some means whereby their simultaneous operation can be controlled without an excessive loss of blood. Further, it happens that various sized drive shafts, having different diameters, may need to be used. Additionally, it may be necessary to change drive shafts or cutters and it may also be necessary to rotate the drive shafts at high rotational speeds for extended periods of time. To help this, the drive shaft and cutter are typically placed inside a catheter sheath which establishes access to the artery and which can extend into the artery to effectively isolate the rotating elements of the atherectomy device from direct contact with any tissue other than the plaque which is to be removed. Despite such precautions, however, blood enters the sheath and, consequently, fluid-tight seals are necesary to prevent the loss of blood through the gaps between the sheath and the rotating drive shaft. Fluid-tight seals must also be maintained while changing drive shafts. As will be appreciated, this can involve moving various drive shafts into and out of the sheath. Accordingly, the specific interest of the present invention is maintaining fluid-tight seals which are necessary for the proper operation of an atherectomy device.
In light of the above, it is an object of the present invention to provide a device for establishing a fluid-tight seal around a rotatable drive shaft which is operable with drive shafts of different diameters. Another object of the present invention is to provide a device for establishing a fluid-tight seal around a rotatable drive shaft which allows drive shafts to be changed or substituted for one another. A further object of the present invention is to provide a device which allows various drive shafts to be changed or substituted one for another without loss of fluid. Still another object of the present invention is to provide a device for establishing a fluid-tight seal around a rotatable drive shaft which can withstand substantial fluid pressures. Yet another object of the present invention is to provide a device for establishing a fluid-tight seal around a rotatable drive shaft which is easy to operate, is relatively easy to manufacture and is comparatively cost-effective.